C # - Search for dictionary keys and search values ​​in a list

Question

In terms of search speed, is it better to look for dictionary keys or list values?

In other words, which one would be most preferable?

Dictionary<tring,string> dic = new Dictionary<string,string>();
if(dic.ContainsKey("needle")){ ... }

or

List<string> list = new List<string>();
if(list.Contains("needle")){ ... }

Answer 1

If “better” means “faster,” use a dictionary. Dictionary keys are organized by hash codes, so search queries are significantly faster than a list search with more than a few elements in ocllection.

O (1), . , O (n), , ( ) .

( ), HashSet. O (1) Value .

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Answer 2

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: http://www.dotnetperls.com/dictionary-time

Answer 3

Dictionary, . List, .

For searches, a dictionary is usually the best choice. The required time is flat, O (1) constant time complexity. The list has a linear time complexity of O (N). Three elements can loop faster than looking in a dictionary.